Production of hexachlorocyclohexane



Allg 19, 1952 J. A. PIANFETTI ErAl.

PRODUCTION OF HEXACHLOROCYCLOHEXANE Filed Jan. 6, 1948 Mm. NN

Sat-entfedi ug. 19, i952 PRODUCTION F HE HE XACHLOROCYCLO- XANE John A. Pianfetti, South Charleston, W. Va., Max

Y. Seaton, Greenwich, Conn., and Dwight Williams, Charleston, W. Va., assignors to Food Machinery and Chemical Corporation, vWilmington, Del., a corporation of Delaware Application January 6, 1948, Serial No. '710 8 Claims. l

This invention relates to an improved process for the production of benzene hexachloride or hexachlorocyclohexaneby the action of chlorine on benzene in the presence of actinic light.

This general process has been known for many years. but substantial experimentation evaluating the prior modes of operation described in the patent and other literature has revealed that there are a number of unsolved problems preventing continuous and most eiicient operation 2 at uniformly high yields. Prior experimentors have suggested undesirably complicated and expensive reaction vessels and internal constructions requiring special procedures for accomplishing efficient contact between the benzene and the chlorine for controlling the temperature and reducing the proportion of by-products formed. Now it has been discovered that the reaction of chlorine with benzene in the presence of actinic light can be expeditiously carried out in very simple apparatus with as great or even greater eiciency than prior processes for the production of hexachlorocyclohexane of high uniform quality.

In one process heretofore suggested. an excess of benzene cooled to a low temperature has been sprayed or flowed in film form countercurrent to a stream of chlorine gas in a reactor illuminated with actinic light whereby hexachlorocyclohexane has been formed in solution in the benzene, after which part of the benzene has been recovered from the process by distillation leaving a residue composed of a concentrated solution of the hexachlorocyclohexane in benzene with various impurities from which the'hexafx It has now been found that this process hasv a number of disadvantages in requiring cooling of the benzene, in reacting at unnecessarily low temperatures, in not completely avoiding deposition Y of hexachlorocyclohexane particularly lin the chlorine inlet intoV the reactor, in using specially constructed means for contacting the chlorine and benzene for obtaining adequate reaction, and especially in employing a crystallizing, settling operation not only leading to segregation'v of the isomers and as a consequence to a lack of uniformity in quality in the final prod-y ucts obtained, but also requiring additional equipment and operations for removing benzene from the crystals, involving both lire and health risks.

Objects of the present invention includeV the desire to provide a process of mixing and reacting chlorine with benzene capable of being carried Aifi out insimple apparatus and capable of operation at higher and more efficient temperatures maintainable by uniform withdrawal of exothermic heat from the reaction mass. Other objects are to produce hexachlorocyclohexane products of uniform isomer and impurity content whereby products of uniform insecticidal properties are produced or can be produced with the minimum of testing.

In accordance with one embodiment of the invention, chlorine and benzene in a sufficient excess to maintain the hexachlorocyclohexane formed in solution are mixed together and thereafter introduced and passed through a reaction Zone illuminated with actinic light and inl contact with cooling surfaces surrounding the zone. While passing through the zone, the benzenechlorine mixture is thoroughly agitated in such manner as to cause all ofthe mass to be adequately exposed to the actinic light and to cause all parts of the mass tok contact frequently and thoroughly with the cooled surfaces thereby to maintain the temperature uniformly at from about 40 to 60 C. After the reaction ofthe benzene with the chlorine has proceeded toa Volatilized at a temperature sutlicient to provide the hexachlorocyclonexane in molten condition.

The volatilized benzene is condensed and rein'- troduced into the reaction zone. The molten hexachlorocyclohexane residue from the distillation is then cooled and solidified most suitably by spreading the same on a cooled surface, from which it is scraped in the form of lianes.

Although it is preferred to carry out the reaction between the chlorine and benzene at a temperature of about 50 C.. the present invention in its broadest scope contemplates the less satis-L factory temperatures of from 10 up to as high as C. Reaction at the preferred tempera:- ture has the advantages, (l) that objectionable amounts of substitution products obtained at higher temperatures are not produced, (2) that the solubility of the hexachlorocyclohexane-product in the benzene is higher than it is at low temperatures, thus permitting the u'se'of less excessl of benzene to be distilled, and (3) that; 4the uniform removal of the heat of reaction isv it reaches the distillation apparatus. When the reaction is carried out at approximately 50 C., the molar ratio of chlorine to benzene employed is approximately 0.25 to 1, the actual combined ratio in hexachlorocyclohexane being 3 to l. At 80 C. a suiiicient excess is provided if the ratio is as high as 2 to 1, Whereas at 10 C. the ratio cannot be much higher than 0.1 to 1.

It is known that hexachlorocyclohexane existsV in the form of at least stereo isomers. Although .one of these isomers, namely the gamma, is more eiective than the others as an insecticide, the presence of other isomers in hexachlorocyclohexane products apparently does no harm. Dilution with inert or less potent powders is conventional. The product of the present invention, containing a substantial proportion of the gamma isomer can therefore be used for insecticidal purposes without resorting to isolation of the gamma isomer. `Since this hexachlorocyclohexane product .is .produced without crystallization .and separation of mother. liquor containingu .dissolved isomers, it isy uniform frombatch to batch .and therefore does not require. extensive .potency tests for. assuring constant quality.

A .preferredv procedure. will.. be. described with reference to the accompanying drawing wherein the apparatus and .connections vare diagrammatically illustrated.

. Chlorine. gas is introduced through aline vI0 into. astreamof .benzene in the .feedline I I lead: ingtoa. nickel standleg I2 terminating near .the bottom of a .reaction vessel or chlorinator I3 jacketed for the. mtroduction. of cool water.. .The interior surface coatinglof. the vessel I3 .orthe vessel itselfl must be .composed .of .material which. does not catalyze the substitution reactionas glass or. nickel, for otherwise undesired substitution .products would be. produced. For. the. same reason .the reactants. shouldbe .relatively pure .or free from catalyzing impurities. Two mercury vapor lamps.. I4. (any;number..can..b.e used). are. mounted in .thetop of ,the .reaction vessel. I3. and extend. substantially to the. bottom thereof. The said reactoris.. provided with a motor operatedy stirring device. or paddles I 5. AIt .will b..e. bserv.ed A

thatthe chlorineand benzene arepremixedin. thedarkor before Vtheyare exposed Vto theactinic lightinthe vessel. Through, this procedureand the; agitation.. of .thereaction massinthe. reactionr vessel, no separationordeposition of hexachlorocyclohexane occurs. Vin ythe. vessel or linestdprevent.continuousoperation The- Iconcurrent now4 of .the reaction 4Iioafss. through.thereactionvessel ismaintairiedata raie..

which brings` aboutsubstarllally.complete reaction of` .all .ofk the, chlorinev introduced into.. the vessel. The reaction massinthe vessell newsfromthe .bottom Ythereof un, and ih roiiehamu.- duitlgto. a `smaller, jackets@ reaction .vessel l l 0i. rc.Q11strulciio.n material similar to. ihereatieii vessel I3, wherein any residualchlqrine c iissolvedl inthe benzene iscompletelr taken unbr reaction in.. themass... This. Supp.leirlsiiiial` reactor .insures ihatne. chlorine. reaches the boiler. wherein Chlorine .substitution riQdiiis. would.. be rrediicedif] ibeciilorine were. present..

.Alfter exposure iq illev mercury reparieren .i4 inthe vessel I'I, the reactionmassows from the tgp'f'thereof 'through a .line I8 to af.distillationd vessel'orreboiler lg'provided'vwith a'jCkt 201er highpressure steamf In. this vessel I9 benzene is distilledfroin .the reactionV massfat a temperature of about`130 C'. 'Ihd vapor. fromthe vessel I9,V passesthrough'the line 2I to a heat exchanger 22 composed suitably of Pyrex glass. The condensed benzene obtained therein ilows through the conduit 23 into a benzene feed tank 24. Fresh benzene from storage is also fed into the tank 24 through the conduit 25.

When distillation of the benzene in the reboiler I9 has proceeded to a point where a hexachlorocyclohexane product containing vabout 10% benzene is obtained, such product is flowed therefrom through the nickel standleg 26 and line 21 to a stripper or supplemental boiler 28 also having a jacket 29 for high pressure steam.

In the stripper the mass is heated to a temperature of about 140 C. under a vacuum suitably of mm. of mercury. The vacuum is applied through a line 3I and a high pressure steamactuated ejector 32. Instead of using a vacuum to vprovide a reduced total pressure, steam or other uid may be directly introduced into the stripper to create a reduced partial pressure.

The evaporation under reduced pressure,.either total or partial, is continued until a hexachlorocyclohexane product is obtainedV containing sub.- stantially no benzene or only up tofabout.0.5%. Thereupon the product,` designated stripped HCCH, which is in molten form is flowed from the boiler or stripper through the conduits .on to a drum aker 34 from. which the cooled. and.v solidied product, designated aked.HCCH,:is removed in the form of fine flakes bythe -usual scraping operation.

Although the benzene distillation temperature is preferably at about C., the presentimention in its broader scope contemplatesall temperatures.. capable of accomplishingfremoval ofthe.

benzene while leaving the hexachlorocyclohexane undisturbed. In any event, atV the conclusion of. the distillation .the hexachlorocyclohexane..prod:- uct should be at, orbrought to a temperaturepof. about C., providing a substantiallybenzene.- free molten massY capable of being. flowed and solidied upon a cooledsurface.

Some of the advantages hereinbefore described for the continuous process may alsobe obtained when the process is operated in` batch-wise fashion. The present Vinvention in its broadest aspects therefore includes, processes, in which a single vessel may be made to serve in succession as the chlorinator,l the boiler and the stripper.

In atypical batch process, Va` jacketedgvessel provided with a stirrer andactinic light source.v is rst chargedl with benzene, then chlorine'isintroduced during stirring;Y and the/, temperatureyis. maintained at 50 C. or withintherange: hereinbefore disclosed. After Va time, the,saturation point of the solution is reached, With.cryst alsof hexachlorocyclohexane beginningv to form.

Thereupon the temperature israised,graciually to some higher temperatureof, orapproaching,V`

80 C. andthe introduction of vchlorine yispzcon-I tinued until the chlorine-benzene. ratio reaches about 2 vto 1. If thetemperature were raised higher than about 80C. additionalchlorine could,n react in the mass, but ordinarily such procedureprocedure, but the -substitution products, if not.

utilized, make this variation uneconomical..

After the chlorination .step is complete,.the, temperature is raised in .order to vaporizeofthe.v

benzene, this result .being .again most satisfactorily accomplished at.130 C. Near the end. of

this vbenzene removal. step,. thepressure..is.re,-

The` present invention dueedin `order toV facilitate the volatilizationof substantially all of the remaining benzeneqBe-y` foreY its solidication, thesmolten hexachlorocyclohexane residue is flowed from the boiler and solidifiedvby spreading'the same on a cool surface in the .manner hereinbefore described. Analysis of theV product Will show that the chlorine has entered the benzenemolecules uniformly at the six carbon atoms, and that its formula is 1, 2, 3, 4, 5, -hexachlorocyclohexane.

In the process hereinbefore described thev excess of benzene called for therein may be replaced in part or Wholly by some inert solvent such as carbon tetrachloride which will maintain in solution the reaction product formed. The use of the inert solvent, however, is not preferred, for it would appreciably complicate theoperation of the process. w K .Y y

It should be understood that the present-invention is not limited to the specific details herein disclosed but that it extends to` all equivalent procedures which will occurV to those skilledin the art upon consideration of the scope of the claims appended hereto.

We claim:

n 1. The `process of producing hexachlorocyclohexane from chlorine and benzene in a liquid phase reaction which comprises mixing chlorine with benzene in an excess adequate to maintain the hexachlorocyclohexane formed in solution, agitating the resulting mixture in a reaction zone irradiated by actinic light at an intensity which causes all parts of the reaction mixture to be thoroughly exposed to the actinic light and repeatedly contacted with the Walls of the reaction zone, maintaining the temperature of the reaction solution substantially uniform by Withdrawing excess exothermic heat from the walls of the zone and after the reaction is substantially complete distilling off the excess benzene at a nal temperature which provides 'the hexachlorocyclohexane in molten form and removing themolten product from the distillation zone and cooling and solidifying the same.

2. The process of producing hexachlorocyclohexane from chlorine and benzene in a liquid phase reaction which comprises mixing chlorine with benzene in the presence of an inert solvent adequate to maintain the hexachlorocyclohexane formed in solution, agitating the resulting mixture in a reaction zone irradiated by actinic light at an intensity which causes all parts of the reaction mixture to be thoroughly exposed to the actinic light and repeatedly contacted with the Walls of the reaction Zone, maintaining the temperature of the reaction solution substantially uniform by withdrawing excess exothermic heat from the Walls of the zone and after the reaction is substantially complete distilling off the solvent with the aid of reduced pressure at a temperature Which provides the hexachlorocyclohexane in molten form and after the molten material has been removed from the distillation zone, cooling and solidifying the same.

3. The process of producing hexachlorocyclohexane frorn chlorine and benzene in a liquid phase reaction which comprises mixing chlorine with benzene in an excess adequate to maintain the hexachlorocyclohexane formed in solution, agitating the resulting mixture in a reaction zone irradiated by actinic light at an intensity which causes all parts of the reaction mixture to be thoroughly exposed to the actinic light and repeatedly contacted with the Walls of the reaction zone, maintaining the temperature of the reaction Solution substantially uniform by ,witi 1 drawing, excess exothermic heat fromv the walls of the zone and after the reaction is substantially complete distilling off most of the benzenecon-l densing the benzene vapors for reuse in the process, vaporizing ofi substantiallyrall of the,4 remaining y Ybenzene from ,thel hexachlorocyclof hexane under partial vacuum.l at a temperature around C. thereby producing'the hexachlorohexane in molten condition,` thereafter cooling and solidifying the hexaehlorocyclohexane.

4. The process of producing `hexachlorocyl?lof hexane from chlorine and benzenein a liquid phase reaction which comprises introducing chlorine, benzene and a solvent adequate to maine tain'the hexachlorocyclohexane formed in `solutioninto a reactingbody of the sainematerials, reacting the added materials under. irradiation by actinic light whereby a solution of hexachlorocyclohexane in the solventis obtained,V recover?V ingthe hexachlorocyclohexane Afrom the solution by distillingoff substantially all lof the solvent at a temperature providing. the hexachlorocyclo-v hexane in molten form, thereafter flowing .the

molten `mass upon a cooled surface thereby solidifying the sameand scraping thev solidified mass from'the surface thereby, providing hexa?. chlorocyclohexane inflaked form. i

5,'The process of producing hexachlorocyclohexane from chlorine and benzene in a liquid phase reaction which comprises mixing chlorine with a body of benzene in an excess adequate to maintain the hexachlorocyclohexane formed in solution, reacting the resulting bodies of reactants under irradiation by actinic light Whereby a solution of hexachlorocyclohexane in benzene is obtained, recovering the hexachlorocyclohexane from the benzene solution by distilling off most of the benzene at atmospheric pressure and vaporizing off substantially all of the remaining benzene at a reduced pressure and at a raised temperature which produces the hexachlorocyclohexane in molten condition and thereafter cooling and solidifying the hexachlorocyclohexane.

6. The process of producing hexachlorocyclohexane from chlorine and benzene in a liquid phase reaction which comprises continuously passing a mixture of chlorine and benzene in an excess adequate to maintain the hexachlorocyclohexane formed in solution, into a reaction zone under irradiation by actinic light, continuously reacting the chlorine with the benzene in the reaction zone thereby forming hexachlorocyclohexane in benzene solution, continuously passing the reaction mass into a distillation zone, continuously distilling oi most of the benzene, and when only a minor amount of benzene remains in the hexachlorocyclohexane passing the same to a heating zone and vaporizing off in said heating zone substantially all of the remaining benzene at a temperature providing the hexachlorocyclohexane in molten form and nally flowing the molten mass from the said heating zone upon a cool surface and solidifying the same, from Which surface the solidified mass can be scraped to provide the hexachlorocyclohexane in flaked form.

7. The process of producing hexachlorocyclohexane from chlorine and benzene in a liquid phase reaction which comprises, mixing chlorine with a body of benzene and a solvent adequate to maintain the hexachlorocyclohexane formed in solution, reacting the same under irradiation by actinic light at a temperature above 10 C. con.-

7 tifmiing-:the 'reactinby iiew'ing benzne, solvent andjchlorineinto said bodyv and ontinuiig'ftfie reaction until hexaelllorooylohxane @is l fonied inl solution in the solvent iecovering'f tlie hia- Chloroc'yclhexa'ne from the solution' bydistllin'g' offl substantially Aall of the solventI presenti atfa temperature providing the YheXahloiot'zy'olomaterial-from the distillationzone; cooling and s'o'ldifying' the same'.

8. Theprooess Vof producing heXael'iloi-oeyelhex-ane whichV eompr'ises; mixing' chlorine with benzene' in an' 'excess adequate to' maintain i tiiehexachlorooyolhexane formed in solution; agi` tating the 'resulting mixture in' areactionzore irradiated by aotinc light at-'ah intensity illiel'i causes allpats 'of the'r'eaction-mixture to-'be thoroughly exposed to the aetinie light and fe'- peatedly contacted-With thwalls ofthefeati zone.- maintaining the reaction solution at an elevated temperature notsubstantially'- inexcess of 60 C! by withdrawing excessexothermic'heat from the walls of thezone and after-the reation is-substantially complete dstilling off the 'excess benzene at' a-final temperature which provides thehexachlorocyolohexane in molten foiin', rel' movingthe'molten pro'duotfrom the di'stillati'cm zone, cooling and' solidifying the4 same by Vilowir'ig OTHER REFERENCES f 

1. THE PROCESS OF PRODUCING HEXACHLOROCYCLOHEXANE FROM CHLORINE AND BENZENE IN A LIQUID PHASE REACTION WHICH COMPRISES MIXING CHLORINE WITH BENZENE IN AN EXCESS ADEQUATE TO MAINTAIN THE HEXACHLOROCYCLOHEXANE FORMED IN SOLUTION, AGITATING THE RESULTING MIXTURE IN A REACTION ZONE IRRADIATED BY ACTINIC LIGHT AT AN INTENSITY WHICH CAUSES ALL PARTS OF THE REACTION MIXTURE TO BE THOROUGHLY EXPOSED TO THE ACTINIC LIGHT AND REPEATEDLY CONTACTED WITH THE WALLS OF THE REACTION ZONE, MAINTAINING THE TEMPERATURE OF THE REACTION SOLUTION SUBSTANTIALLY UNIFORM BY WITHDRAWING EXCESS EXOTHERMIC HEAT FROM THE WALLS OF THE ZONE AND AFTER THE REACTION IS SUBSTANTIALLY COMPLETE DISTILLING OFF THE EXCESS BENZENE AT A FINAL TEMPERATURE WHICH PROVIDES THE HEXACHLOROCYCLOHEXANE IN MOLTEN FORM AND REMOVING THE MOLTEN PRODUCT FROM THE DISTILLATION ZONE AND COOLING AND SOLIDIFYING THE SAME. 